One of the more challenging aspects of learning how to play jazz is that it requires someone to build a repertoire of techniques and vocabulary, but at the same time to learn how to interact with other musicians, and their conceptual ideas regarding harmony and rhythm, etc. It's a journey both inward and outward, in other words. One way that jazz musicians practice on their own (which is how nearly all their work is done - most serious jazz musicians rehearse very little) is with the use of play-along CDs. These are recordings of rhythm sections (bass and drums, with piano or guitar) playing the backing tracks for songs, but which leave room for the user to play the melody and to improvise through many repetitions (or choruses, as they're known) of the piece. These help to bridge the gap between the personal, introspective aspects of jazz with the collective ones which require paying close attention to outside information. (The best-known provider of these recordings is Jamey Aebersold. Here's a link to his Wikipedia page, if you want to know more: http://en.wikipedia.org/wiki/Jamey_Aebersold.)

The reason that I'm bringing this up is a very interesting project that has been put together by the great guitarist, Pat Metheny, which was certainly inspired by devices such as the player-piano, but which may also have a debt to play-along recordings. It is known as the Orchestrion project, and you can read and view about its nature, much better than I could explain it, here: http://www.patmetheny.com/orchestrioninfo/ . It strikes me as a very interesting development in the combination of human and technological elements in music, because it permits the musician to improvise, and to create the setting for it, simultaneously. As a concept, its potential is limitless; check it out.